RFID radio frequency identification or property monitoring method and associated apparatus

Abstract

A method of identifying an article of interest includes providing one of a plurality of RF antennas each having a non-linear element which may be a rectifying diode and being resident at a different frequency on the article of interest. One RF antenna is interrogated with RF energy of a first frequency and converts the interrogated RF energy into a reflected energy of a different frequency. The reflected energy is sensed and on the basis of the different frequency determining if a specific antenna is present. The non-linear element may be a diode and is preferably a variable non-linear element. In another embodiment, the reflected RF energy is responsive to a change in ambient physical conditions such as pressure or temperature. Corresponding apparatus is provided.

1. A method of identifying an article of interest, comprising:
 providing one of a plurality of RF antennas each having a non-linear element and being resonant at one of a plurality of different frequencies positioned on an article of interest, 
 interrogating said one RF antenna with RF energy of a first frequency, 
 converting said interrogating RF energy into reflected RF energy of a different frequency from said first frequency, 
 sensing said reflected RF energy, 
 determining a difference between said first frequency and said different frequency by subtracting one of said first frequency and said different frequency from the other of said first frequency and said different frequency, and 
 on the basis of said difference between said first frequency and said different frequency determining if a specific said antenna is present. 
 
   
   
     2. The method of  claim 1  including said non-linear element is a rectifying diode. 
   
   
     3. The method of  claim 2  including said specific antenna is present and said different frequency being about double said first frequency. 
   
   
     4. The method of  claim 1  including said one RF antenna providing a half wave rectified sine wave from said interrogating RF energy. 
   
   
     5. The method of  claim 4  including said interrogating RF energy producing a sine wave. 
   
   
     6. The method of  claim 4  including said half wave rectified sine wave has a fundamental Fourier series which is about double the frequency of said sine wave. 
   
   
     7. The method of  claim 1  including employing two said interrogating frequencies in determining if an article of interest is present. 
   
   
     8. The method of  claim 7  including employing a spectrum analyzer in analyzing said different frequency. 
   
   
     9. The method of  claim 7  including employing a spectrum analyzer structured to monitor each interrogating frequency in determining if an article of interest is present. 
   
   
     10. The method of  claim 1  including employing a binary analysis in determining if an article of interest is present. 
   
   
     11. The method of  claim 10  including employing said method to provide specific identification of the antenna if an article of interest is present. 
   
   
     12. The method of  claim 1  including a second non-linear element cooperating with said non-linear element to provide a variable readout which is a function of a specific physical condition. 
   
   
     13. The method of  claim 12  including employing as said non-linear elements a variable non-linear element. 
   
   
     14. The method of  claim 1  including said physical condition being a condition selected from the group consisting of pressure, temperature, pH, chemical concentrations and humidity, chemical environment, biological environment, radiation, and light. 
   
   
     15. Apparatus for determining if an article of interest is present, comprising:
 said article of interest having at least one antenna, one of said at least one antenna being resonant at one frequency of a plurality of available frequencies, 
 a non-linear element operatively associated with said one of said at least one antenna, 
 an RF frequency generator for directing RF energy of a particular frequency to said one of said at least one antenna, said non-linear element causing said one of said at least one antenna to transmit reflected RF energy in response to receipt of said RF energy, said reflected RF energy having a reflected frequency that is different than said directed particular frequency, 
 a detector for receiving said reflected RF energy from said one of said at least one antenna, and 
 a processor adapted to determine a difference between said directed particular frequency and said reflected frequency by subtracting one of said directed particular frequency and said reflected frequency from the other of said directed particular frequency and said reflected frequency and to determine from a said difference between said reflected frequency and said directed particular frequency whether the one of said at least one antenna is a specific antenna. 
 
   
   
     16. The apparatus of  claim 15  including said non-linear element being a rectifying diode. 
   
   
     17. The apparatus of  claim 16  including said RF frequency generator being structured to provide at least two said interrogating RF frequencies. 
   
   
     18. The apparatus of  claim 16  including a spectrum analyzer for analyzing said different frequencies. 
   
   
     19. The apparatus of  claim 16  including a second non-linear element cooperating with said non-linear element to provide a variable readout which is a function of a specific physical condition. 
   
   
     20. The apparatus of  claim 19  including said physical condition being a condition selected from the group consisting of pressure, temperature, pH, chemical concentrations, humidity, chemical environment, biological environment, radiation, and light. 
   
   
     21. The apparatus of  claim 15  including said RF frequency generator being structured to produce interrogating RF energy in the form of a sine wave. 
   
   
     22. The apparatus of  claim 21  including said one of said at least one antenna being structured to produce a half wave rectified sine wave from said interrogating RF energy. 
   
   
     23. The apparatus of  claim 22  including said one of said at least one antenna being structured to provide said half wave rectified sine wave at a fundamental Fourier series component which is about double the frequency of said sine wave. 
   
   
     24. A method of monitoring an ambient physical property, comprising:
 providing an antenna having a non-linear element whose response depends on the physical property being monitored, 
 interrogating said RF antenna with RF energy of a first frequency, 
 converting the interrogating RF energy into reflected RF energy of a different frequency from said first frequency, said different frequency being dependent on the physical property being monitored, 
 sensing said reflected RF energy, 
 determining a difference between said first frequency and said different frequency by subtracting one of said first frequency and said different frequency from the other of said first frequency and said different frequency, and 
 on the basis of said difference between said first frequency and said different frequency determining the state of said physical property. 
 
   
   
     25. The method of  claim 24  wherein said non-linear element is a rectifying diode. 
   
   
     26. The method of  claim 25  wherein said different frequency being about double said first frequency. 
   
   
     27. The method of  claim 24  including said antenna providing a half wave rectified sine wave from said interrogating RF energy. 
   
   
     28. The method of  claim 27  including said interrogating RF energy producing a sine wave. 
   
   
     29. The method of  claim 27  including said half wave rectified sine wave has a fundamental Fourier series which is about double the frequency of said sine wave. 
   
   
     30. The method of  claim 24  including employing a spectrum analyzer in analyzing said different frequency. 
   
   
     31. The method of  claim 24  including employing a second non-linear element cooperating with said non-linear element to provide a determination regarding whether an article of interest is present. 
   
   
     32. The method of  claim 24  including said ambient physical property being a condition selected from the group consisting of pressure, temperature, pH, chemical concentrations and humidity, chemical environment, biological environment, radiation, and light. 
   
   
     33. Apparatus for monitoring an ambient physical property, comprising:
 an antenna being resonant at one frequency of a plurality of available frequencies, 
 a non-linear element operatively associated with said antenna whose response depends on the physical property being monitored, 
 an RF frequency generator for directing RF energy at a particular frequency to said antenna, said non-linear element causing said antenna to transmit reflected RF energy in response to receipt of said RF energy, said reflected RF energy having a reflected frequency that is different than said directed particular frequency and that is dependent on the physical property being monitored, 
 a detector for receiving said reflected RF energy from said antenna, and 
 a processor adapted to determine a difference between said particular frequency and said reflected frequency by subtracting one of said particular frequency and said reflected frequency from the other of said particular frequency and said reflected frequency and to determine from a said difference between said particular frequency and said reflected frequency the state of the physical property being monitored. 
 
   
   
     34. The apparatus of  claim 33  including said non-linear element being a rectifying diode. 
   
   
     35. The apparatus of  claim 34  including said RF frequency generator being structured to provide at least two said interrogating RF frequencies. 
   
   
     36. The apparatus of  claim 34  including a spectrum analyzer for analyzing said different frequencies. 
   
   
     37. The apparatus of  claim 34  including a second non-linear element cooperating with said non-linear element to provide a variable readout which is a function of said physical property. 
   
   
     38. The apparatus of  claim 37  including a second non-linear element cooperating with said non-linear element to provide a variable readout which is a function of said physical property. 
   
   
     39. The apparatus of  claim 33  including said RF frequency generator being structured to produce interrogating RF energy in the form of a sine wave. 
   
   
     40. The apparatus of  claim 39  including said antenna being structured to produce a half wave rectified sine wave from said interrogating RF energy. 
   
   
     41. The apparatus of  claim 40  including said antenna being structured to provide said half wave rectified sine wave at a fundamental Fourier series component which is about double the frequency of said sine wave.